java - Hibernate OneToMany List 或 Iterator 不同？

Question

@Entity
@Table(name = "STUDENT")
public class Student {

    private long studentId;
    private String studentName;
    private List<Phone> studentPhoneNumbers;

    ....

    @OneToMany(cascade = CascadeType.ALL)
    @JoinTable(name = "STUDENT_PHONE", joinColumns = { @JoinColumn(name = "STUDENT_ID") }, inverseJoinColumns = { @JoinColumn(name = "PHONE_ID") })
    public List<Phone> getStudentPhoneNumbers() {
        return this.studentPhoneNumbers;
    }

    public void setStudentPhoneNumbers(List<Phone> studentPhoneNumbers) {
        this.studentPhoneNumbers = studentPhoneNumbers;
    }
}

1)

Student student = session.loadStudent(123); // pseudocode
List phoneList = student.getStudentPhoneNumbers();
for (Phone p : phoneList) {
    ...
}

2)

Student student = session.loadStudent(123); // pseudocode
List phoneList = student.getStudentPhoneNumbers();
Iterator itr = phoneList.iterator();   
while(itr.hasNext()) {
    ...
}

我从这里阅读了答案:difference between query.list and query.iterate

显然，list() 和 iterator() 之间存在差异(在 Query 中)。如果我在 OneToMany 列表中使用它会怎样？就像上面的例子，性能上有区别吗？内存？

Answer 1

与 Hibernate 无关。

当Java编译器遇到

for (Phone p : phoneList) {
    ....
}

它自动生成相当于

的代码

for (Iterator<Phone> itr = phoneList.iterator(); itr.hasNext();) {
    Phone p = itr.next();
    ....
}

因此，您所展示的两个示例本质上是相同的。